How to refresh applied fonts?
Through the interface there is currently no way to replace the file for an existing font (ideally this would be supported),however from Python you can do this.

eg, run this script:

import bpy
bpy.context.object.data.font.filepath = '//some_font.ttf'


However in 2.76 there is a bug where this won't update immediately (just fixed).

So you have to do...

import bpy
bpy.context.object.data.font.filepath = '//some_font.ttf'
bpy.context.object.data.update_tag()


You could set the file-path to its self to force reloading too.